The release of inflammatory cytokines such as tumor necrosis factor-alpha (TNFxcex1) by leukocytes is one means by which the immune system combats pathogenic invasions, including infections. Cytokines stimulate neutrophils to enhance oxidative (e.g., superoxide and secondary products) and nonoxidative (e.g., myeloperoxidase and other enzymes) inflammatory activity. Inappropriate and over-release of cytokines can produce counterproductive exaggerated pathogenic effects through the release of tissue-damaging oxidative and nonoxidative products (Tracey, K. G. et al., J. Exp. Med., 167, 1211-1227 (1988); and Mxc3xa4nnel, D. N. et al., Rev. Infect. Dis., 9 (suppl 5), S602-S606 (1987)).
For example, inflammatory cytokines have been shown to be pathogenic in: arthritis (Dinarello, C. A., Semin. Immunol., 4, 133-45 (1992)); ischemia (Seekamp, A. et al., Agents-Actions-Supp., 41, 137-52 (1993)); septic shock (Mxc3xa4nnel, D. N. et al., Rev. Infect. Dis., 9 (suppl 5), S602-S606 (1987)); asthma (Cembrzynska Nowak M. et al., Am. Rev. Respir. Dis., 147, 291-5 (1993)); organ transplant rejection (Imagawa, D. K. et al., Transplantation, 51, 57-62 (1991)); multiple sclerosis (Hartung, H. P., Ann. Neurol., 33, 591-6 (1993)); and AIDS (Matsuyama, T. et al., AIDS, 5, 1405-1417 (1991)). In addition, superoxide formation in leukocytes has been implicated in promoting replication of the human immunodeficiency virus (HIV) (Legrand-Poels, S. et al., AIDS Res. Hum. Retroviruses, 6, 1389-1397 (1990)).
It is well known that adenosine and some adenosine analogs that non-selectively activate adenosine receptor subtypes decrease neutrophil production of inflammatory oxidative products (Cronstein, B. N. et al., Ann. N.Y. Acad. Sci., 451, 291-314 (1985); Roberts, P. A. et al., Biochem. J., 227, 669-674 (1985); Schrier, D. J. et al., J. Immunol., 137, 3284-3289 (1986); Cronstein, B. N. et al., Clinical Immunol. and Immunopath., 42, 76-85 (1987); Iannone, M. A. et al., in Topics and Perspectives in Adenosine Research, E. Gerlach et al., eds., Springer-Verlag, Berlin, 286-298 (1987); McGarrity, S. T. et al., J. Leukocyte Biol., 44, 411-421 (1988); De La Harpe, J. et al., J. Immunol., 143, 596-602 (1989); McGarrity, S. T. et al., J. Immunol., 142, 1986-1994 (1989); and Nielson, C. P. et al., Br. J. Pharmacol., 97, 882-888 (1989)). For example, adenosine has been shown to inhibit superoxide release from neutrophils stimulated by chemoattractants such as the synthetic mimic of bacterial peptides, f-met-leu-phe (fMLP), and the complement component C5a (Cronstein, B. N. et al., J. Immunol., 135, 1366-1371 (1985)). Adenosine can decrease the greatly enhanced oxidative burst of PMNs (neutrophils) first primed with TNFxcex1 (an inflammatory cytokine) and then exposed to a second stimulus such as f-met-leu-phe (Sullivan, G. W. et al., Clin. Res. 41, 172A (1993)). There is evidence that in vivo adenosine has anti-inflammatory activity (Firestein, G. S. et al., Clin. Res., 41, 170A (1993); and Cronstein, B. N. et al., Clin. Res., 41, 244A (1993)). Additionally, it has been reported that adenosine can decrease the rate of HIV replication in a T-cell line (Sipka, S. et al., Acta. Biochim. Biopys. Hung., 23, 75-82 (1988)).
It has been suggested that there is more than one subtype of adenosine receptor on neutrophils that have opposite effects on superoxide release (Cronstein, B. N. et al., J. Clin. Invest., 85, 1150-1157 (1990)). The existence of the A2A receptor on neutrophils was originally demonstrated by Van Calker et al. (Van Calker, D. et al., Eur. J. Pharmacology, 206, 285-290 (1991)).
There has been progressive development of compounds that are more and more potent and selective as agonists of A2A adenosine receptors based on radioligand binding assays and physiological responses. Initially, compounds with little or no selectivity for A2A receptors were used, such as adenosine itself or 5xe2x80x2-carboxamides of adenosine, such as 5xe2x80x2-N-ethylcarboxamidoadenosine (NECA) (Cronstein, B. N. et al., J. Immunol., 135, 1366-1371 (1985)). Later it was shown that addition of 2-alkylamino substituents increased potency and selectivity, e.g., CV1808 and CGS21680 (Jarvis, M. F. et al., J. Pharmacol. Exp. Ther., 251, 888-893 (1989)). 2-Alkoxy-substituted adenosine derivatives such as WRC-0090 are even more potent and selective as agonists on the coronary artery A2A receptor (Ukena, M. et al., J. Med. Chem., 34, 1334-1339 (1991)). The 2-alkylhydrazino adenosine derivatives, e.g., SHA 211 (also called WRC-0474) have also been evaluated as agonists at the coronary artery A2A receptor (Niiya, K. et al., J. Med. Chem., 35, 4557-4561 (1992)).
There is one report of the combination of relatively nonspecific adenosine analogs, R-phenylisopropyladenosine (R-PIA) and 2-chloroadenosine (Cl-Ado) with a phosphodiesterase (PDE) inhibitor resulting in a lowering of neutrophil oxidative activity (Iannone, M. A. et al., in Topics and Perspectives in Adenosine Research, E. Gerlach et al., Eds., Springer-Verlag, Berlin, 286-298 (1987)). However, R-PIA and Cl-Ado analogs are actually more potent activators of Al adenosine receptors than of A2A adenosine receptors and, thus, are likely to cause side effects due to activation of A1 receptors on cardiac muscle and other tissues causing effects such as xe2x80x9cheart blockxe2x80x9d.
Linden et al. (U.S. Pat. No. 5,877,180) is based on the discovery that inflammatory diseases may be effectively treated by the administration of drugs which are selective agonists of A2A adenosine receptors, preferably in combination with a phosphodiesterase inhibitor. An embodiment of the Linden et al. invention provides a method for treating inflammatory diseases by administering an effective amount of an A2A adenosine receptor of the following formula: 
wherein X is a group selected from the group consisting of xe2x80x94OR1, xe2x80x94NR2R3, and xe2x80x94NHxe2x80x94Nxe2x95x90R4;
wherein R1 is C1-4-alkyl; C1-4-alkyl substituted with one or more C1-4-alkoxy groups, halogens (fluorine, chlorine or bromine), hydroxy groups, amino groups, mono(C1-4-alkyl)amino groups, di(C1-4-alkyl)amino groups or C6-10-aryl groups (wherein the aryl groups may be substituted with one or more halogens (fluorine, chlorine or bromine), C1-4-alkyl groups, hydroxy groups, amino groups, mono(C1-4-alkyl)amino groups or di(C1-4 alkyl)amino groups); C6-10-aryl; or C6-10-aryl substituted with one or more halogens (fluorine, chlorine or bromine), hydroxy groups, amino groups, mono(C1-4-alkyl)amino groups or di(C1-4-alkyl)amino groups or C1-4-alkyl groups;
one of R2 and R3 has the same meaning as R1 and the other is hydrogen;
R4 is a group having the formula: 
wherein each of R5 and R6 independently may be hydrogen, C3-7-cycloalkyl or any of the meanings of R1, provided that R5 and R6 are not both hydrogen; and
R is xe2x80x94CH2OH, xe2x80x94CH2H, xe2x80x94CO2R7 or xe2x80x94C(xe2x95x90P)NR8R9; wherein R7 has the same meaning as R1 and wherein R8 and R9 have the same meanings as R5 and R6 and R8 and R9 may both be hydrogen.
In a preferred embodiment, the Linden et al. invention involves the administration of a Type IV phosphodiesterase (PDE) inhibitor in combination with the A2A adenosine receptor agonist. The Type IV phosphodiesterase (PDE) inhibitor can be racemic and optically active 4-(polyalkoxyphenyl)-2-pyrrolidones of the following formula: 
(disclosed and described in U.S. Pat. No. 4,193,926) wherein R18 and R19 each are alike or different and are hydrocarbon radicals having up to 18 carbon atoms with at least one being other than methyl, a heterocyclic ring or alkyl of 1-5 carbon atoms which is substituted by one or more of halogen atoms, hydroxy, carboxy, alkoxy, alkoxycarbonyl or an amino group; amino; Rxe2x80x2 is a hydrogen atom, alkyl, aryl or acyl; and X is an oxygen atom or a sulfur atom.
Rolipram is an example of a suitable Type IV phosphodiesterase or PDE inhibitor included within the above formula. Rolipram has the following structure: 
The present invention provides a method to protect mammalian tissue from the effects of the inflammatory response. This treatment is achieved by the administration of certain agonists of A2A adenosine receptors, preferably in combination with Rolipram or Rolipram derivatives that are Type IV phosphodiesterase or PDE inhibitors.
Accordingly, one aspect of the present invention is to provide a novel and improved method for treating the inflammatory response to pathological agents and conditions, such as trauma.
It is another aspect of the present invention to provide novel and improved compositions for the treatment of the inflammatory response and, in some cases, the underlying disease.
It is another aspect of the present invention to provide novel and improved compositions for the treatment of the inflammatory response, which are rapidly metabolized or broken down to provide less active or inactive metabolites when they come in contact with blood or other physiological fluids.
It is another aspect of the present invention to provide compounds that are short acting coronary vasodilatators for pharmacological stress imaging
These and other aspects, which will become better understood during the course of the following detailed description, have been achieved by the inventors"" discovery of improved compositions and methods for effectively treating inflammatory conditions by administration of an agonist of an A2A adenosine receptor optionally, in combination with Rolipram or a Rolipram derivative that is a Type IV phosphodiesterase (PDE) inhibitor.